Air filter and filter media thereof

ABSTRACT

A filter media can include a fiber coated with a barrier coating that is substantially non-reactive to reactive species, and a photocatalytic coating disposed on the barrier coating, wherein the photocatalytic coating generates reactive species in response to illumination with optical radiation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/463,271 filed 31 Aug. 2021, which claims the benefit of U.S.Provisional Application No. 63/072,676, filed 31 Aug. 2020, each ofwhich is incorporated in its entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the fluid filtration field, and morespecifically to a new and useful system and method in the fluidfiltration field.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of the system.

FIG. 2 is a schematic representation of an example of a cross section ofa photocatalyst disposed on a coating disposed on a substrate.

FIGS. 3A and 3B are schematic representations of examples of compositesubstrates.

FIGS. 4A and 4B are schematic representations of examples ofphotocatalyst disposed on a coating disposed on a substrate.

FIG. 5 is a graphical representation of an example percent weight changeof control samples (e.g., made of filter media material), uncoatedfilter media including photocatalytic material, and coated filter mediaincluding photocatalytic material, each illuminated with ultravioletradiation (e.g., substantially equivalent doses such as irradiance,duration, wavelength, etc.).

FIG. 6 is a schematic representation of an example of a filter mediaintegrated into a multilayer filter.

FIGS. 7A, 7B, 7C, and 7D are schematic representations of examplesconductive material loading on a barrier coated fiber.

FIGS. 8A, 8B, and 8C are schematic representations of examples ofdisposing photocatalyst on a barrier coated fiber.

FIG. 9 is a schematic representation of an exemplary air filtrationsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. OVERVIEW

As shown in FIG. 1 , the filter media 10 can include a substrate 100 andphotocatalytic material 300. The filter media can optionally include oneor more coatings 200, 200′. The filter media can optionally beintegrated into (e.g., mounted in, attached to, etc.) an air purifier,an HVAC system, a ventilation system, and/or any suitable fluidfiltration or purification system.

The filter media 10 preferably functions to remove contaminants from afluid (e.g., air, water, etc.). The filter media is preferablyconfigured to degrade (e.g., destroy) the contaminants (e.g., oxidizingand/or reducing the contaminants into byproducts such as carbon dioxideand/or water), but can additionally or alternatively trap (e.g.,capture) contaminants and/or otherwise remove contaminants from thefluid. Examples of contaminants can include: volatile organic compounds(VOCs, such as terpenes, aromatic compounds, aliphatic compounds, etc.),particulate matter (e.g., microparticles, mesoparticles, macroparticles,nanoparticles, etc.), organic matter (e.g., pollen, mold, spores,bacteria, viruses, etc.), inorganic matter (e.g., nitrogen oxides (NOx),sulfur oxides (SO_(x)), etc.), allergens (e.g., pet fur, dander, dust,etc.), and/or any suitable contaminants.

The filter media can be integrated into and/or used as a layer of amultilayer filter (e.g., as disclosed in U.S. patent application Ser.No. 16/523,928 entitled ‘FLUID FILTRATION SYSTEM AND METHOD OF USE’filed on 26 Jul. 2019 which is incorporated in its entirety by thisreference), used as a standalone filter media, and/or can otherwise beused and/or integrated into any suitable media.

In a preferred embodiment as shown for example in FIG. 9 , the filtermedia can be incorporated into a fluid purification system 20. The fluidpurification system can include a housing 23 that defines a lumen (e.g.,including a fluid flow path, an inlet, and an outlet), a light source 22(e.g., UV light source, visible light source such as incandescentsources, light emitting diodes, lasers, sunlight, fluorescent lamps, gasdischarge lamps, phosphors, nonlinear sources, etc.) configured toilluminate photocatalytic material of the filter media, a supportstructure (e.g., to retain the filter media, the light source, etc.), animpeller 21 configured to urge fluid through the fluid purificationsystem (e.g., along the fluid flow path), and/or any suitablecomponents. The light source preferably illuminates the filter mediawith at least about 100 W/m2 (e.g., 100 W/m², 150 W/m², 200 W/m², 250W/m², 300 W/m², 400 W/m², 500 W/m², 1000 W/m², 5000 W/m², valuestherebetween, >5000 W/m²) of optical radiation (e.g., UV radiation suchas UV-A, UV-B, and/or UV-C radiation; visible radiation; infraredradiation; etc.), but can illuminate the filter media and/orphotocatalytic material thereof with less than 100 W/m² (e.g., <1 W/m²,1 W/m², 2 W/m², 5 W/m², 10 W/m², 20 W/m², 50 W/m², 100 W/m², etc.) ofoptical radiation. The light source can operate continuously and/orintermittently. For example, the light source can continually illuminatethe filter media over a time span of minutes, hours, days, weeks,months, years, decades, and/or any suitable time span (e.g., withoutdetecting filter or substrate degradation). In an illustrative example,an air purification system can be arranged as and/or include anycomponents as disclosed in U.S. patent application Ser. No. 16/870,301entitled ‘SYSTEM AND METHOD FOR PHOTOELECTROCHEMICAL AIR PURIFICATION’filed on 8 May 2020 or U.S. patent application Ser. No. 17/152,690entitled ‘FLUID FILTRATION SYSTEM AND METHOD OF USE’ filed on 19 Jan.2021, each of which is incorporated in its entirety by this reference.However, the filter media can be used in isolation and/or in any system.

2. BENEFITS

Variations of the technology can confer several benefits and/oradvantages.

First, variations of the technology can increase the lifetime of thefilter media and can enable less expensive filter substrates to be used(e.g., wherein conventional uses of such substrates in an uncoatedmanner would otherwise experience unacceptable levels of chemical and/orphotochemical degradation). The lifetime of the filter media can beincreased, for example, by hindering, slowing, and/or preventingdegradation of substrates (e.g., polymeric substrates, natural fibers,synthetic organic materials, etc.) in reactive (e.g., oxidative)environments. In a specific example, as shown in FIG. 5 , uncoatedfilter media exposed to reactive environments (e.g., in photocatalyticoxidation conditions) lose mass whereas coated (e.g., barrier coated)filter media exposed to substantially the same reactive environment arelargely unaffected by the reactive environment (e.g., do not lose mass).

Second, variations of the technology can enable higher light sourceintensities to be apply and/or used to illuminate the photocatalyticmaterial, which can improve an efficiency (e.g., kinetics ofdegradation, degree of degradation, single pass efficiency, time toachieve a target contaminant level within a given volume, etc.). Forexample, typically photocatalytic filters are operated at most withapproximately 50 W/m² of illumination to extend a lifetime of the filter(e.g., to prevent degradation of the filter due to either directreactions at the filter caused by light or indirect reactions initiatedby the photocatalyst). Using a barrier coated or other filter mediawhere the photocatalytic material is in contact with inorganic species,an illumination intensity that is greater than about 100 W/m² can beused (e.g., for extended periods of time such as months to years withoutobserving significant breakdown or degradation of the filter).

Third, variations of the technology can enable biodegradable,photocatalytic filter media to be formed. The inventors have discoveredthat biodegradable fibers (e.g., made of a biodegradable polymer such aspoly(lactic acid) (PLA), polycaprolactone, polybutylene succinate,polybutylene succinate adipate, aliphatic-aromatic copolyesters,polybutylene adipate/terephthalate, polymethylene adipate/terephthalate,etc.; cellulose; silk; wool; keratin; etc.) will rapidly break down whenin proximity to active photocatalysts (e.g., illuminatedphotocatalysts). By applying a barrier coating to the biodegradablefiber protects (e.g., increases a lifetime of, hinders or preventsdegradation of, etc.) the fiber from the photocatalytic material. At theend of life (e.g., due to poisoning of the photocatalyst, fiberdegradation, filter clogging, etc.), the barrier coated fiber can bebiodegraded (e.g., by crushing the filter media to expose the barriercoated fibers to a natural environment enabling the fibers to degrade).By using a barrier coating and/or photocatalytic material derived fromminerals (e.g., silica, silicate, borate, sand, metal oxides, etc.), thefilter media can be biodegradable (e.g., compostable). Variations ofthis example can form a completely biodegradable filter by using, inaddition to biodegradable fibers, a biodegradable material (that ispreferably barrier coated) as filter end caps. However, no end caps canbe provided, recyclable end caps can be used (e.g., made of metal,glass, long-lived polymers, etc. such that the fibers can be removed andreplaced within the end caps), and/or renewable and/or green filters canotherwise be formed.

However, variants of the technology can confer any other suitablebenefits and/or advantages.

3. FILTER MEDIA

As shown in FIG. 1 , the filter media 10 can include a substrate 100 andphotocatalytic material 300. The filter media can optionally include oneor more coatings 200, 200′. The filter media preferably functions toremove contaminants from a fluid.

The filter media 10 (and/or components thereof) is preferably configuredto allow fluid (e.g., contaminant laden fluid) to pass through themedia. For example, the filter media can be porous, include definedholes and/or channels for fluid to flow through, include a plurality offibers (e.g., interwoven fibers), and/or have any suitable geometry orstructure to promote fluid flow through the filter media (e.g., flowrate>0 m³/s). However, the filter media can additionally oralternatively be configured to promote fluid flow over the surface ofthe media (e.g., configured to bring contaminants in contact with and/orproximity to photocatalytic material), and/or be otherwise configured.In variants, filters made with the filter media can have a minimumefficiency reporting value (MERV) score between 1-20. The MERV score candepend on the coating (e.g., the coating material, the coatingthickness, the coating porosity, the coating structure, etc.), coatingprocess, substrate (e.g., the substrate material fiber size, fiberdensity, etc.), the photocatalytic material (e.g., morphology,thickness, material, size, etc.), and/or otherwise depend on the filtermedia. In an illustrative example, the uncoated substrate can correspondto or be associated with a first MERV score (e.g., based on a porosity,pore size, fiber density, etc.) and the coated substrate can correspondto or be associated with a second MERV score (e.g., based on a coatingthickness, based on a coating material, additives, etc.), where thesecond MERV score is higher than the first MERV score. However, the MERVscore can be otherwise determined.

A broad face (e.g., surface) of the filter media can be pleated, smooth(e.g., flat), folded, ridged, puckered, curved, a mixture of features,and/or the broad face can have any suitable configuration. Preferably,all of the layers of the filter media have the same broad faceconfiguration; however, each of the layers can have different broad faceconfigurations (e.g., different sizes such as different pleating depth,different configurations, etc.), a subset of the layers can have thesame broad face configuration, the layers can have a broad faceconfiguration that depends on adjacent layers (e.g., layer type, layerbroad face, layer contaminant removal mechanism, etc.), and/or any othersuitable layer broad face configuration can be used. In a specificexample, the pleating depth (e.g., average peak to trough size of thepleats), can be determined based on (e.g., vary directly or inverselywith): filter media size, filter media surface area, the intendedapplication (e.g., airflow filtration, oil filtration, water filtration,office filtration, home filtration, automobile, etc.), fluid flow rate,and/or any other suitable parameter. In examples, the pleating depth canbe any depth (or range thereof) between 0.1 cm-50 cm, and/or have anyother suitable depth. The pleat density can be: between 1-10 pleats per100 mm or range thereof, 5 pleats per 100 mm, or any other suitablepleat density.

A form factor of the filter media can be cylindrical, hemispherical,planar (e.g., square, rectangular, circular, elliptical, oval, etc.),hemicylindrical, spherical, prismatoidal (e.g., being shaped like acuboid, triangular prism, prismoid, etc.), toroidal, ellipsoidal,catenoidal, and/or have any other suitable geometry.

In some embodiments, the filter media (e.g., a substrate, coating,electrically conductive material, photocatalytic material, or othercomponent thereof) can be electrostatically charged. This electrostaticcharge can function to electrostatically attract contaminants to thefilter media. The filter media is preferably positively charged (e.g.,to attract negatively charged contaminants), but can be negativelycharged (e.g., to attract positively charged contaminants), have regionsof positive and negative charge, have a variable charge (e.g., beswitchable between a positive and negative charge such as using an ACelectric potential, which can have the benefit of reversibly storing andreleasing contaminants to balance a contaminant load), and/or have aneutral charge. The electrostatic charge can be generated by thesubstrate, one or more coatings (e.g., a barrier coating, a dielectriccoating, etc.), the photocatalytic material, and/or otherwise begenerated. The electrostatic charge can be actively generated (e.g., byapplying or maintaining an electric potential to a material) and/orpassively generated (e.g., generated due to static electricity). In somevariants, one or more additives can be included (e.g., in the substrate,in the coating(s)) to increase the duration and/or extent of chargebuild-up. Exemplary additives include: stearate, high dielectricmaterials (e.g., barium titanate BaTiO₃), mercaptobenzimidazolate salts,fatty acids, fatty acid amides, oleophobic surfactants, fluorochemicalsurfactants, oleophobic fluorochemical surfactants, and/or any suitablecharge extending and/or enhancing additives can be used. In somevariants, the electrostatic charge can be beneficial for thephotocatalytic process, for example by increasing the lifetime ofseparated electrons and holes, by increasing a rate or efficiency ofelectron/hole separation, increase a rate and/or efficiency ofgeneration of reactive species, and/or otherwise improve thephotocatalytic process. However, the electrostatic charge may bedetrimental to and/or not impact the photocatalytic process.

The substrate 100 preferably functions to support photocatalyticmaterial 300. The substrate can additionally or alternatively capture(e.g., mechanically, electrostatically, etc.) one or more contaminants,conduct energy (e.g., electricity, heat, etc.), and/or perform anyfunction. The substrate can be made of (e.g., composed of, composedessentially of, etc.) organic material (which can be beneficial forlow-cost manufacturing processes and materials, are often lighter thaninorganic materials, etc.), inorganic material (which can be beneficialfor greater resistance to degradation), and/or combinations thereof(which can combine benefits of each material). The substrate can befibrous (e.g., constructed of fibers 130 such as interwoven fibers,fibers as disclosed in U.S. patent application Ser. No. 17/074,368entitled ‘FLUID DISINFECTION DEVICE AND METHOD’ filed on 19 Oct. 2020which is incorporated in its entirety by this reference, etc.), porous,solid, and/or otherwise constructed. A fiber size (e.g., diameter,thickness, length, etc.) can be between about 1 μm and 100 cm (such as 1μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 500 μm, 1 mm, 2 mm,5 mm, 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 50 cm, 100 cm, valuestherebetween), can be less than 1 μm, and/or greater than 100 cm.

The substrate can be translucent (example shown in FIG. 6 ),transparent, opaque, or otherwise refract or scatter one or more lightwavelengths (e.g., UV, IR, visible light, etc.). The substratepreferably transmits at least 20% of incident optical radiation (e.g.,at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, 99%, 99.5%, 99.9%,etc.) is transmitted through the substrate and/or fibers or othercomponents thereof. This can be beneficial for increasing lightpenetration into and/or an intensity of optical radiation within thesubstrate which can enable photocatalytic material in the interior ofthe substrate can be illuminated and contribute to the photocatalyticreactions. For example, optical radiation (e.g., UV radiation, visibleradiation, infrared radiation, etc.) can penetrate (e.g., retain atleast a threshold irradiance such as at least 1 W/m², 2 W/m², 5 W/m², 10W/m², 20 W/m², 50 W/m², 100 W/m², values therebetween, >100 W/m², <1W/m², etc.) through at least 5% of the filter media thickness (e.g., 5%,10%, 20%, 25%, 30%, 50%, 75%, 80%, 90%, 95%, 100%), can penetrate lessthan 5% of the filter media thickness, can penetrate a predetermineddistance through the filter media (e.g., 100 μm, 200 μm, 500 μm, 1 mm, 2mm, 5 mm, 1 cm, 2 cm, 5 cm, 10 cm, values therebetween, <100 μm, >10 cm,etc.), and/or through any suitable portion of the filter media. Thepenetration depth or distance can depend on a photocatalyst loading,photocatalyst scattering coefficient (e.g., absorption coefficient),substrate transparency or translucency, coating transparency ortranslucency, a wavelength of the optical radiation, and/or canotherwise depend on any suitable features or properties.

The substrate and/or constituents thereof can have a surface roughnessbetween about 25 nm and 50 μm such as 25 nm, 50 nm, 100 nm, 200 nm, 500nm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, or values therebetween; asurface roughness less than 25 nm; a surface roughness greater than 50μm; and/or any suitable surface roughness. In variants, a coating canincrease a smoothness of the substrate (e.g., the coated substrate canhave a smaller surface roughness than the uncoated substrate) and/ordecrease a smoothness of the substrate (e.g., the resulting material canhave a larger surface roughness than the underlying substrate). However,the coated substrate can have substantially the same surface roughnessas the underlying substrate and/or any suitable surface roughness.

Examples of organic materials include: polymers (e.g., polypropylene(PP), polyethylene (PE), cellulose, poly(lactic acid), polycaprolactone,polybutylene succinate, polybutylene succinate adipate,aliphatic-aromatic copolyesters, polybutylene adipate/terephthalate,polymethylene adipate/terephthalate, poly(hydroxybutyrate),poly(hydroxyvalerate), polyhydroxyhexanoate, poly(hydroxyalkanoates),cyclic olefin copolymer (COC), poly (methyl methacrylate),polyamide-imide, polyimide, fluorinated ethylene propylene, styrenemethyl methacrylate, perfluoropolymers, etc.), fabrics (e.g., wovenfabrics, non-woven fabrics), paper, and/or any suitable organicmaterial. Examples of inorganic materials include: glass (e.g., silicaglass), metals (e.g., aluminium, steel, copper, zinc, nickel, etc.)and/or compounds thereof (e.g., metal oxides), ceramics, and/or anysuitable inorganic materials. Embodiments of the substrate that include(e.g., are composed essentially of, consist essentially of, include to asubstantial amount) one or more of: poly(lactic acid), polycaprolactone,polybutylene succinate, polybutylene succinate adipate,aliphatic-aromatic copolyesters, polybutylene adipate/terephthalate,polymethylene adipate/terephthalate, poly(hydroxybutyrate),poly(hydroxyvalerate), polyhydroxyhexanoate, poly(hydroxyalkanoates)and/or other suitable materials, can provide the benefit of forming abiodegradable substrate and/or filter media. Embodiments of thesubstrate that include (e.g., are composed essentially of, consistessentially of, include to a substantial amount) one or more of: cyclicolefin copolymer (COC), poly (methyl methacrylate), polyamide-imide,polyimide, Fluorinated Ethylene Propylene, Styrene Methyl methacrylate,perfluoropolymers, and/or other suitable materials can provide thebenefit of forming a UV transparent substrate and/or filter media.However, any suitable polymers and/or combination of polymers can beused (e.g., to impart target chemical, mechanical, electrical,recyclability, etc. properties).

In variants including combinations of organic and inorganic materials,the organic and inorganic materials can be integrated (e.g., to form acomposite material), layered (e.g., stacks of organic and/or inorganicmaterials in any order), and/or otherwise interfaced with each other. Ina first illustrative example as shown in FIG. 3A, the substrate caninclude a first polymer layer 157 adjacent to (e.g., in contact with) aglass layer 153 (e.g., a first surface of the glass layer) which isadjacent to (e.g., in contact with) a second polymer layer 157′ (e.g.,at a second surface of the glass layer). The first and second polymerlayers can be in contact or separated (e.g., by the glass layer) fromone another. The first and second polymer layers can be or include thesame or different polymer(s). In a second illustrative example, as shownin FIG. 3B, the substrate can include a glass layer 153 in contact witha polymer layer 157. In these illustrative examples, the polymerlayer(s) can provide structural support to the glass layer (and/orfilter media). However, the substrate can be otherwise arranged.

The optional coating(s) 200 can function to facilitate (e.g., improve)adherence of the photocatalyst to the substrate, modify theelectrostatic properties of the substrate, hinder or prevent reactivespecies (e.g., contaminant, byproducts, reactive species generated bythe photocatalyst, etc.) from contacting the substrate, increase aseparation lifetime of electron/hole pairs, increase a rate orefficiency of separating electron/hole pairs, increase a lifetime of thesubstrate, and/or can perform any function. Coating(s) that hinder orprevent the reactive species from contacting or reacting with thesubstrate can be referred to as “barrier coatings.” However, barriercoatings can be otherwise defined. The filter media can include one ormore coatings. Each coating can be the same or different (e.g., performthe same of different functions).

The coating(s) can conformally coat the substrate (and/or the underlyingconstituents thereof) and/or underlying coating(s), coat in a pattern(e.g., regions with coating and regions without coating, regions withhigher density of coating and regions with lower density of coating,based on a filter media structure, etc.), can nonconformally coat and/orcan otherwise coat the substrate. The coating(s) can cover the entireexposed surface of the substrate and/or underlying coatings, a subset ofthe exposed surface of the substrate (e.g., specific materials of thesubstrate, specific locations of the substrate, etc.) and/or underlyingcoatings, a predetermined extent of the substrate and/or underlyingcoatings and/or otherwise cover the substrate and/or underlyingcoatings. For instance, each fiber (of a fibrous substrate) can beindividually coated with the coating material, fibers can be coatedtogether (e.g., sealing a gap or space between the fibers), a surface ofeach fiber can be coated (e.g., an upstream or downstream surfacerelative to a fluid flow direction, relative to an optical illuminationdirection, etc.), and/or the fiber(s) can otherwise be coated. At leastone coating (e.g., the outermost coating of a coating stack) ispreferably in contact with (e.g., touches) the photocatalytic material.

The coating(s) can be uniform (e.g., vary in thickness and/or coverageacross the substrate by at most about 20%, are smooth, etc.), nonuniform(e.g., are rough; have a characteristic surface roughness that iscomparable to a characteristic size of the photocatalytic material; havea surface roughness between about 25 nm and 50 μm such as 25 nm, 50 nm,100 nm, 200 nm, 500 nm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, or valuestherebetween; surface roughness less than 25 nm; surface roughnessgreater than 50 μm; etc.), have a predetermined pattern or structuralvariation (e.g., matching and/or based on an illumination pattern),and/or otherwise cover the substrate. Nonuniform variants of the coatingcan function to increase the (exposed) surface area of the coating andcan enable increased photocatalytic material loading and/or increase thenumber of reactive sites for interacting with contaminants. In anillustrative example, as shown in FIG. 4A, the coating can define asand-like surface (e.g., a nonuniform surface made of many differentsites with different thicknesses or sizes). However, the coating candefine any suitable surface.

Each coating can have any thickness between about 1 nm and 1 μm (such as2 nm, 5 nm, 10 nm, 20 nm, 25 nm, 50 nm, 100 nm, 200 nm, 500 nm, valuestherebetween, etc.). However, one or more coatings can be thinner than10 nm (e.g., to enable or impart a target optical absorbance ortransmittance of the coating) or thicker than 1 μm. In some variants,for example as shown in FIG. 2 , the thickness of the coatings (e.g.,the total thickness of all the coatings, the thickness of a givencoating, etc.) can be chosen to modify the porosity, pore size, MERVscore, and/or other properties of the filter media. In a specificexample, the coating thickness is preferably between about 10 nm (whichcan be beneficial to minimize or avoid pinholes or otherwise ensure thatthe coating fully protects or coats the underlying substrate and/orcoatings) and 200 nm (which can be beneficial as thicker coatings canimpact the mechanical properties of the substrate or coating, can beharder to work with, can be too rigid, etc.). In this specific example,the minimum and/or maximum coating thicknesses can depend on thesubstrate, on the coating (e.g., material), the coating process, atarget coating property (e.g., transparency, optical absorption,electrical conductivity, mechanical property, flexibility, rigidity,etc.), and/or otherwise be determined.

In variants including more than one coating, coatings can be stacked(e.g., disposed on top of each other), adjacent to each other,overlapping, and/or otherwise be arranged. Each coating can be discrete,intermixed, embedded within another coating, and/or otherwise be relatedto each other.

The coating(s) are preferably barrier coatings 250 such as coatings thatare substantially impervious to (e.g., do not react with, reacts lessthan a threshold amount with, react at a rate less than a thresholdrate, etc.) and/or impenetrable to the fluid, contaminants, byproducts,reactive species, light, and/or other species that can be formed duringand/or found in proximity to the filter media (e.g., during filter mediause). In particular, the barrier coating is preferably resistant to(e.g., does not react with, reacts at a rate less than a threshold rate,forms a benign species upon reaction, does not react with at roomtemperature, does not react with at an operation temperature of thefilter media, etc.) reactive oxygen species (e.g., superoxide, excitedoxygen, oxygen radicals, ozone, etc.), hydroxyl radicals, hydrogenradicals, and/or other radical or ionic species that can be formed bythe photocatalytic material. However, the coating(s) may be porous,and/or be otherwise permeable to the fluid, contaminants, byproducts,reactive species, and/or other species that can be formed during and/orfound in proximity to the filter media.

The coating(s) are preferably transparent to UV radiation (e.g.,transparent to radiations corresponding to wavelengths and/or rangesthereof between 100-400 nm). The coatings preferably transmit at least50% (e.g., 60%, 70%, 80%, 90%, 95%, 99%, 99.9%, etc.) of UV radiation(e.g., light or optical radiation with a wavelength between 100-400 nmor any wavelength or subrange therein such as 315-400 nm, 250-315 nm,100-250 nm, UV-A, UV-B, UV-C, etc.). However, the coatings can transmitless than 50% of UV radiation (e.g., 5%, 10%, 20%, 30%, 40%, 50%, etc.).However, the coating can additionally or alternatively scatter, reflect,absorb, and/or otherwise optically interact with the UV radiation. Thecoating(s) can be transparent to, translucent to, scatter, reflect,absorb, and/or otherwise optically interact with visible radiation(e.g., radiation with wavelengths between about 400 and 800 nm),infrared radiation (e.g., radiation with wavelengths greater than about800 nm), and/or any suitable electromagnetic radiation.

Coating(s), particularly but not exclusively those in contact withphotocatalytic material, are preferably inorganic (e.g., made ofinorganic material, composed essentially of inorganic material, consistessentially of inorganic material, etc.), but can be organic (e.g.,include organic material, include scavengers and/or other sacrificialspecies that preferentially react with reactive species generatedproximal the photocatalyst), and/or composite (e.g., including organicand inorganic materials, include a mixture of organic materials, includea mixture of inorganic materials).

Examples of coating materials include: polymers (e.g., conductivepolymers such as polyacetylene, polyphenylene vinylene, polypyrrole,polythiophene, polyaniline, polyphenylene sulfide,poly(3,4-ethylenedioxythiophene), Poly(4,4-dioctylcyclopentadithiophene), etc.; insulating polymers such as cellulose, PE,PP, polyethylene terephthalate (PET), etc.; etc.), metals (e.g.,aluminium, stainless steel, zinc, titanium, copper, nickel, etc.), metaloxides (e.g., transparent conductive oxides such as indium tin oxide(ITO), fluorine doped indium tin oxide (FTO), etc.; conductive oxides;semiconducting oxides such as titanium oxides, zinc oxides, etc.;insulating oxides; etc.), glass (e.g., liquid glass, silica, silicates,borosilicate, fused silica, borate glass, borates such as B₂O₃, etc.),zeolites, ceramics, inorganic carbon (e.g., graphite; graphene;fullerenes; carbon nanotubes such as semiconducting nanotubes, metallicnanotubes, combinations thereof, etc.), and/or any materials. However,any suitable coating material(s) can be used. In some variants, acoating (particularly but not exclusively glass or silicate coatings)can include (e.g., mixed, doped with, embedded with, etc.) boron oxides(e.g., boron trioxide B₂O₃, boron monoxide B₂O, boron suboxide B₆O,etc.), borates (e.g., diborate, triborate, tetraborate, etc.), and/orany suitable components or additives. In these variants, the amount ofadditive (e.g., borate, boron oxides, etc.) is preferably 1-20% (e.g.,by weight, by mass, by volume, etc.), but can be less than 1% or greaterthan 20%.

One or more coatings can be electrically conductive (e.g., have anelectrical conductivity meeting or exceeding a threshold conductivity),electrically insulating (e.g., have an electrical conductivity that isat most a threshold conductivity), dielectric, semiconducting, and/orhave any suitable electrical properties.

In some embodiments, one or more coating can be oxidized (e.g., duringoperation, during manufacture, during shipping, during substratecoating, etc.). For example, metal coatings (such as Zn and/or Cu) canbe oxidized to metal oxides (e.g., zinc oxide, copper oxide,semiconducting metal oxides, etc.; partially oxidized such as surfaceoxidation; etc.) which can in turn be photocatalytic (e.g., function asphotocatalytic material such as described below) and/or function asantimicrobial agent.

In some embodiments, particularly but not exclusively when the filtermedia (e.g., substrate, coating) includes a polymeric material (such asPET), the substrate and/or coating(s) can be metallized (e.g., be dopedwith metal, include metal, include metal nanoparticles, reacted with ametal, electroless metal deposition, etc.), which can function to modify(e.g., increase) the electrical properties of the substrate and/orcoating such as to prepare or provide an electrically-conductive coating(e.g. with electrically conductivity exceeding a threshold). In specificexamples, the substrate and/or coating(s) can be metallized with (and/orthe metallization process can be catalyzed by) a noble metal (e.g.,copper, silver, gold), a transition metal, and/or any suitable metal.However, the coating (or substrate) can be intrinsically electricallyconductive and/or the electrical conductivity or the coating can beotherwise modified.

The photocatalytic material 300 preferably functions to generate one ormore reactive species to react with (e.g., oxidize, reduce) one or morecontaminants in the fluid. Examples of reactive species include hydroxylradicals, hydrogen radicals, reactive oxygen species (e.g., superoxide,excited oxygen, oxygen radicals, ozone, etc.), radical anions, radicalcations, and/or any suitable reactive species. The photocatalyticmaterial is preferably in contact with and/or proximal to (e.g., withina threshold distance of) only inorganic material of the substrate and/orcoatings. However, the photocatalytic material can be in contact withand/or proximal to (e.g., within a threshold distance of) organicmaterial and/or any suitable material of the substrate and/or coatings.The photocatalytic material can be disposed on a surface of thesubstrate and/or coating (e.g., a surface proximal a contaminant ladenfluid, an external environment, etc.; as shown for example in FIG. 8A;etc.), integrated into the coating and/or substrate (e.g., intercalatedinto pores of the coating or substrate, as shown for example in FIG. 8Bor 8C, etc.), located at an interface between a coating and thesubstrate, located at an interface between two coatings, and/or can beotherwise arranged.

The photocatalytic material can be coupled chemically (e.g., covalentlybonded, ionically bonded, metallically bonded, via a coupling agent,etc.), physically (e.g., adsorbed, absorbed, electrostatically,magnetically, etc.), and/or otherwise be coupled to the substrate and/orcoating(s). For example, the photocatalytic material can be embedded ina coating. In a second example, the photocatalytic material can beadhered to the coating such as using a binder (e.g., an inorganicbinder, an organic binder, a binder and/or adhesive as disclosed in U.S.patent application Ser. No. 17/378,973 entitled ‘FILTER MEDIA AND SYSTEMAND METHOD FOR MANUFACTURE THEREOF’ filed on 19 Jul. 2021 which isincorporated in its entirety by this reference, etc.). However, thephotocatalytic material can otherwise be coupled to the substrate and/orcoatings.

The photocatalytic material is preferably, but does not have to be,coupled to an electrically conductive material.

In variants where the photocatalytic material is embedded in a coating,at most about 10% (e.g., <0.1%, 0.1%, 0.5%, 1%, 2%, 2.5%, 3%, 5%, 7%,9%, 10%, values therebetween, as shown for example in FIG. 8B, etc.) ofthe surface are of the photocatalytic material is preferably embedded inthe coating. However, greater than 10% (e.g., 20%, 30%, 50%, 75%, 80%,90%, 100%, values therebetween, etc.; as shown for example in FIG. 8C;etc.) of the surface area of the photocatalytic material can be embeddedin the coating, photocatalytic material can be disposed on the coating(and/or substrate; as shown for example in FIG. 8A), and/or thephotocatalytic material can otherwise be disposed on, in, or proximal acoating and/or substrate.

The photocatalytic materials can be provided as a film (e.g., thin film,thick film), quantum dots, nanostructures, nanocrystals, particles(e.g., nanoparticles, mesoparticles, microparticles, nanoporousparticles, microporous particles, mesoporous particles, etc.), and/or inany suitable form factor. When the photocatalytic material is nanoscale(e.g., quantum dots, nanoparticles, nanocrystals, nanostructures, etc.),a characteristic size (e.g., diameter, length, width, height, distancebetween grains, etc.) of the photocatalytic material is preferablybetween about 25-50 nm, but can be smaller than 25 nm or greater than 50nm. In some variants, particularly but not exclusively when nanoscalephotocatalytic materials are used, the photocatalytic material canagglomerate, aggregate, and/or otherwise form clusters of photocatalyticmaterial. The clusters of photocatalytic material are typically betweenabout 300 nm and 500 μm in size, but can be smaller than 300 nm orlarger than 500 μm. Cluster formation can be controlled (e.g.,mitigated, hindered, enhanced, etc.) using surfactants, ultrasound,and/or other methods.

The photocatalytic materials are preferably photoelectrochemicaloxidative (e.g., PECO) materials, but can additionally or alternativelybe photoelectrochemical (PEC) materials, and/or any suitablephotocatalytic materials. The photocatalytic material can includeinorganic or organic species. The photocatalytic material can include(e.g., be made of) one or more of: titanium oxide, zinc oxide, sodiumtantalite, carbonaceous materials (e.g., inorganic carbon such as carbonnanotubes, graphite, graphene, amorphous carbon, etc.; organic carbonsuch as polymers, surfactants, etc.; etc.), transition metals and metaloxide, and/or any suitable materials. For instance, the photocatalyticmaterial can be composed or consist essentially of inorganicmaterial(s). In specific examples, the photocatalytic materials caninclude and/or correspond to any suitable materials as disclosed in U.S.patent application Ser. No. 16/777,454 entitled “SYSTEM AND METHOD FORPHOTOELECTROCHEMICAL AIR PURIFICATION” filed 30 Jan. 2020, and/or U.S.Pat. No. 7,635,450 entitled “PHOTOELECTROCHEMICAL AIR DISINFECTION”filed on 26 Apr. 2006 each of which is herein incorporated in itsentirety by this reference. However, any photocatalytic material can beused.

The filter media preferably includes electrically conductive material260 (e.g., a material with an electrical conductivity meeting orexceeding a threshold; material with a valance band that is higher thanthe valence band of the photocatalytic material, a material with aconduction band that is lower than the conduction band of thephotocatalytic material; form a Type 1, Type 2, or Type 3 heterojunctionwith the photocatalytic material; form a metal-semiconductor junctionwith the photocatalytic material with a Schottky barrier less than athreshold such as approximately k_(B)T; etc.). The electricallyconductive material can be embedded in a coating, embedded in thesubstrate, embedded in the photocatalytic material, disposed on acoating, disposed on the substrate, disposed on the photocatalyticmaterial, form a coating (e.g., on another coating such as on a barriercoating, on the substrate, on the photocatalytic material, etc.), and/orcan otherwise be disposed.

The electrically conductive material is preferably electrically coupledto the photocatalytic material, but can be electrically isolated fromthe photocatalytic material and/or otherwise be connected ordisconnected from the photocatalytic material. For example, electricallyconductive material is preferably within a threshold distance (e.g., 1nm, 2 nm, 5 nm, 10 nm, etc. where distance can be an average distance, amaximum distance, an RMS distance, or other distance) of photocatalyticmaterial. However, the electrically conductive material can beelectrically coupled to the photocatalytic material in any manner (e.g.,using wires, using electrically conductive paths, be within a Förster orFRET distance of the photocatalytic material, be within a dextertransfer distance of the photocatalytic material, be within a quantumtunneling range of the photocatalytic material, etc.).

The electrically conductive material can be homogeneously distributedand/or heterogeneously (e.g., inhomogeneously) distributed. As shown forexample in FIGS. 7A-7D, electrically conductive material can behomogeneously distributed throughout a coating, heterogeneouslydistributed within a coating (e.g., proximal a surface of the coatingwhere photocatalytic material is disposed, within a threshold distanceof a surface of the coating, etc.), forms islands on the coating, bepatterned on the coating (e.g., to match a structure of the filter mediasuch as a pleating, to match an illumination pattern, etc.), and/or canotherwise be distributed.

The electrically conductive materials can be a film (e.g., thin film,thick film, etc.), particles (e.g., nanoparticles, mesoparticles,macroparticles, etc.; where a particle shape can be spheroidal,nonspheroidal, star, rod, tube, pyramidal, etc.), form islands (e.g., asshown for example in FIG. 7C), and/or have any suitable morphology. Acharacteristic size (e.g., thickness, diameter, radius, longitudinalextent, lateral extent, etc.) of the electrically conductive materialscan be picoscale (e.g., <1 nm), nanoscale (e.g., between about 1-500nm), mesoscale (e.g., between about 500-5000 nm), microscale (e.g.,between about 1 μm and 100 μm), macroscale (e.g., >100 μm), spanmultiple size scales, and/or can be any suitable size. The electricallyconductive materials can be amorphous, crystalline (e.g.,monocrystalline, polycrystalline, etc.), glassy, and/or have anysuitable packing density or structure.

The electrically conductive material preferably transmits (e.g., allowslight to pass through, allows light to pass between or around adjacentelectrically conductive material, etc.) at least 50% (e.g., 60%, 70%,80%, 90%, 95%, 99%, 99.9%, etc.) of radiation (e.g., UV radiation with awavelength between 100-400 nm or any wavelength or subrange therein suchas 315-400 nm, 250-315 nm, 100-250 nm, UV-A, UV-B, UV-C, etc.; visibleradiation with a wavelength or range thereof between about 400-800 nm;infrared radiation; etc.). However, the electrically conductive materialcan transmit less than 50% of UV radiation (e.g., 5%, 10%, 20%, 30%,40%, 50%, etc.). The optical properties of the electrically conductivematerial can be achieved by tuning a characteristic size (e.g.,thickness, radius, diameter, longitudinal extent, lateral extent, etc.)of the material, based on a material selection (e.g., specific material,mixture of materials, material doping, etc.), based on an area ofcoverage (e.g., a coverage density of the electrically conductivematerial), and/or can otherwise be determined. In a first illustrativeexample, a transparent or translucent conductive film can be formed byusing a 10 nm (or thinner) silver film. In a second illustrativeexample, an inorganic carbon (e.g., graphene, carbon nanotubes, etc.)can be used to form a transparent or translucent conductive film. In athird illustrative example, a metallic grid can be used to form atransparent or translucent film (e.g., where light passes through gapsin the grid such that the percentage of the film that forms gaps isapproximately equal to the percentage of light transmitted). In a fourthillustrative example, islands of electrically conductive material can beformed on the substrate and/or coating. The islands (e.g., nonconnectingpatches, films, surfaces, etc. of electrically conductive material)preferably cover about 0%-50% of the underlying material and therebyallow 100%-50% of incident light to pass the island. However, theislands of material can cover any suitable portion of the surface.However, a transparent or translucent conductive material can otherwisebe formed.

Examples of electrically conductive materials include: ITO, FTO, dopedzinc oxide, copper, zinc, tin, aluminium, nickel, silver, gold,graphene, graphite, nanowire meshes, metal grids, carbon nanotubes,aluminium oxynitride, conductive polymers, topological insulators (e.g.,where a surface of the material is electrically conductive), and/or anysuitable conductive material(s) can be used.

The coatings can be made and/or the substrate can be coated using dipcoating, spin coating, deposition (e.g., chemical vapor deposition,physical vapor deposition, etc.), spray coating, brushing, flow coating,electrolysis, electroplating, roll-to-roll coating processes, and/orusing any suitable process. In some variants (for example to formislands and/or otherwise dispose electrically conductive material on acoating), a material can be physically embedded into a coating or thesubstrate (e.g., using polishing, grinding, impingement, etc.) followedby plating the material. In these variants, the physically embeddedmaterial can act analogously to a nucleation site to enable plating ofthe material when it may not typically be possible. In a specificexample of this variant, metal particles (e.g., aluminium particles,copper particles, zinc particles, etc.) can be embed or implanted in aglass (e.g., silicate) coating. In this specific example, metal islandscan be grown using electroplating (e.g., from the sites of the metalparticle implantation or embedding), electrolytic deposition, and/or anysuitable method.

The method of manufacture can include curing the coating and/oradhesives which can function to solidify, harden, improve a structuralintegrity of, improve a chemical resistance of, dry the coating and/oradhesive, and/or can otherwise function. Exemplary curing processesinclude: desiccation or dehydration (such as by providing or blowing dryair over a surface of the materials, applying a vacuum to the materials,heating the materials, etc.), annealing the materials, chemicallytreating the materials, radiatively treating the materials, and/or usingany suitable curing or treatment process. The curing process can occurinstantly (e.g., upon mixing or applying the curing process), after acuring time has elapsed (e.g., after the curing process has beenperformed for a curing time, with a delay after the curing process hasbeen performed, etc.), and/or with any suitable timing.

In some embodiments, coatings, electrically conductive material,photocatalytic material, and/or any suitable materials can be added orapplied before a prior layer or material has finished curing (e.g.,annealing, before a full curing time has elapsed, etc.). Theseembodiments can function to embed, implant, and/or otherwise mix orincorporate materials into distinct layers. For example, while (such asafter a predetermined time that is less than the curing time has passed)a glass (e.g., silicate) coating is being cured (e.g., hardening),photocatalytic particles 350 can be disposed on the glass coating whichcan embed (and/or adhere) the photocatalytic particles in the glasscoating. The extent to which the photocatalytic particles are embeddedcan depend on the coating material, the photocatalytic material, thepredetermined time, the time remaining before the curing time haselapsed, the curing method, and/or can otherwise be determined.Variations of this specific example can be used to embed electricallyconductive material in a coating. However, materials (e.g.,photocatalytic material, electrically conductive material, etc.) can beadded contemporaneously with coating materials, and/or any suitablematerial(s) can be embedded in a coating in any manner.

The filter media can optionally include a frame, which can function toretain and/or support the filter media (e.g., to define a geometry orstructure of the filter media). The frame can surround the filter media,surround a perimeter of the filter media, be adjacent to one or moreedge of the filter media, and/or otherwise be related to a portion ofthe filter media. In a specific example, a frame for cylindrical filtermedia can be an end cap (e.g., one end cap on each end of the media suchas a circular or annular end cap). The frame can be made of the sameand/or different materials from the filter media. For instance,biodegradable polymers can be used to make the frame enabling abiodegradable filter (e.g., by using biodegradable polymers for thesubstrate). Similarly, UV transparent polymers could be used to make theframe enabling a UV transparent filter. Alternatively, UV-blockingpolymers or materials can be used for the frame to prevent or hinderlight from leaking out of the filter by the frame. However, the framecan be made of any suitable material(s).

3. ILLUSTRATIVE EXAMPLES

In a first illustrative example, the filter media can include an organicsubstrate coated with an electrically conductive coating (e.g., polymercoating, metallized coating, etc.), with photocatalytic materialdisposed on the electrically conductive coating (e.g., in contact withonly the polymer coating).

In a second illustrative example, the filter media can include anorganic substrate with a barrier coating (e.g., composed essentially ofsilica; made of another inorganic material), an electrically conductivecoating (e.g., in contact with a surface of the barrier coating opposingthe substrate, in contact with a surface of the barrier coating proximalthe substrate, etc.), and photocatalytic material coupled to theelectrically-conductive coating.

In a third illustrative example as shown in FIG. 4B, the filter mediacan include an organic substrate coated with a barrier coating, andphotocatalytic material disposed on a surface of the barrier coatingopposing the organic substrate.

In a fourth illustrative example, the filter media can includephotocatalytic material disposed on an inorganic substrate.

In a fifth illustrative example, the filter media can include aninorganic substrate coated with an electrically conductive coating andphotocatalytic material disposed on the electrically conductive coating.

In a sixth illustrative example, the filter media can include acomposite substrate 150 including one or more glass layers 153 and oneor more polymer layers 157 (e.g., PET, PP, etc.) and photocatalyticmaterial. In this example, the photocatalytic material can be disposedon the glass layer(s) (e.g., only in contact with glass layers), thepolymer layer(s) (e.g., only in contact with the polymer layers), and/ora combination thereof (e.g., in contact with both glass and polymer ofthe substrate).

In a seventh illustrative example, the filter media can include acomposite substrate, a barrier coating (e.g., disposed on organicmaterials of the substrate such as polymeric layers, disposed on theentire substrate, etc.), and photocatalytic material (e.g., disposed onthe barrier coating, disposed on the substrate, disposed only oninorganic constituents of the substrate, etc.). In related examples, thefilter media can additionally or alternatively include an electricallyconductive coating.

In an eighth illustrative example, the filter media can include afibrous polymeric substrate, wherein a fiber of the substrate is coatedwith an inorganic barrier coating (e.g., a glass such as a silicatecoating). Photocatalytic material (e.g., photocatalytic particles) canbe disposed on the inorganic barrier coating. The inorganic barriercoating can be between about 10-200 nm thick and can be substantiallyuniform along the fiber. An electrically conductive coating can beincluded where the electrically conductive coating can be the same asthe inorganic barrier coating, can coat the substrate, can coat theinorganic barrier coating, and/or can otherwise be disposed. In avariation of this specific example, the photocatalytic particles can beembedded in the inorganic barrier coating. At most 10% of thephotocatalytic particle surface area is preferably embedded in theinorganic barrier coating.

In a ninth illustrative example, a filter media can include a fibrouspolymeric substrate, wherein a fiber of the substrate is coated with aninorganic barrier coating (e.g., a glass such as a silicate coating).Photocatalytic material (e.g., photocatalytic particles) can be disposedon the inorganic barrier coating. The inorganic barrier coating can bebetween about 10-200 nm thick and can be substantially uniform along thefiber. An electrically conductive material (e.g., metal particles,nanotubes, inorganic carbon, etc.) can be included where theelectrically conductive material can be disposed on the barrier coating,disposed on the substrate, disposed on the photocatalytic material, beembedded within the inorganic barrier coating (e.g., homogeneouslydistributed within, embedded within a threshold distance of a surface ofthe barrier coating or photocatalytic material, etc.), and/or canotherwise be arranged. In a variation of this specific example, thephotocatalytic particles can be embedded in the inorganic barriercoating (e.g., in addition to the embedded electrically conductivematerial).

Embodiments of the system and/or method can include every combinationand permutation of the various system components and the various methodprocesses, wherein one or more instances of the method and/or processesdescribed herein can be performed asynchronously (e.g., sequentially),concurrently (e.g., in parallel), or in any other suitable order byand/or using one or more instances of the systems, elements, and/orentities described herein.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A hybrid filter comprising: a photocatalytic layercomprising: a fibrous substrate wherein fibers of the fibrous substrateare coated with a barrier coating, wherein the fibers are composedessentially of a polymer, wherein the fibers are at least 80%transparent to UV-A optical radiation; and photocatalytic particlesdisposed on the barrier coating of the fibrous substrate; and a sorbentlayer in contact with the photocatalytic layer, the sorbent layercomprising activated carbon disposed on a second substrate.
 2. Thehybrid filter of claim 1, wherein the sorbent layer is contacted to thephotocatalytic layer using an adhesive.
 3. The hybrid filter of claim 1,wherein the polymer comprises polymethyl methacrylate.
 4. The hybridfilter of claim 1, wherein the barrier coating comprises a silicateglass.
 5. The hybrid filter of claim 4, wherein the barrier coating isbetween about 10 and about 200 nm thick.
 6. The hybrid filter of claim4, where the barrier coating is inert to gas phase reactive oxygenspecies.
 7. The hybrid filter of claim 1, wherein about 10% of a surfacearea of the photocatalyst particles is implanted in the barrier coating.8. The hybrid filter of claim 1, wherein the fibrous substrate achievesa first MERV rating, wherein the photocatalytic layer achieves a secondMERV rating, wherein the second MERV rating is greater than the firstMERV rating.
 9. The hybrid filter of claim 8, wherein the second MERVrating is at least
 16. 10. The hybrid filter of claim 1, wherein thephotocatalytic layer further comprises electrically conductive materialin electrical contact with the photocatalytic particles, wherein theelectrically conductive material is disposed on at most 50% of a surfacearea of the fibrous substrate.
 11. A filter media comprising: a fibroussubstrate, wherein fibers of the fibrous substrate are coated with abarrier coating that is inert to gaseous reactive oxygen species,wherein the fibrous substrate is at least 80% transparent to ultravioletoptical radiation; and photocatalytic particles disposed on the barriercoating, wherein the photocatalytic particles form reactive oxygenspecies in the presence of ultraviolet optical radiation.
 12. The filtermedia of claim 11, further comprising a conductive material disposed onthe barrier coating and in electrical communication with thephotocatalytic particles.
 13. The filter media of claim 12, wherein theconductive material comprises metal particles, wherein the metalparticles cover at most 50% of a surface area of the fibrous substrate.14. The filter media of claim 11, wherein a photocatalytic particle isimplanted in the barrier coating, wherein at most 10% of a surface areaof the photocatalytic particle is implanted in the barrier coating. 15.The filter media of claim 11, wherein the photocatalytic particlecomprises at least one of anatase titanium dioxide, rutile titaniumdioxide, sodium tantalite, or zinc oxide.
 16. The filter media of claim11, wherein the fibrous substrate comprises polymethylmethacrylate. 17.The filter media of claim 11, wherein a thickness of the barrier coatingis between about 10 nm and about 200 nm.
 18. The filter media of claim17, wherein the barrier coating conformally coats the fibers of thefibrous substrate
 19. The filter media of claim 11, wherein the fibroussubstrate and the photocatalytic particles cooperatively form aphotocatalytic layer, the filter media further comprising a sorbentlayer in contact with and distinct from the photocatalytic layer. 20.The filter media of claim 19, wherein the sorbent layer comprises asecond substrate with activated carbon disposed on the second substrate21. The filter media of claim 19, wherein the sorbent layer is adheredto the photocatalytic layer.
 22. The filter media of claim 11, whereinthe fibrous substrate comprises a MERV score of at least 16.